Nd3+ induces three-dimensional hierarchical rosette-shaped Bi3O4Br to generate abundant oxygen vacancies for enhanced photocatalytic activity

[Display omitted] •Three-dimensional hierarchical rosette-shaped Bi3O4Br was successfully prepared for the first time.•Doping Nd3+ in the matrix of Bi3O4Br induces a large number of oxygen vacancies and triggers energy band hybridization.•The doping energy levels exacerbate the inhomogeneity of the charge distribution and accelerate charge separation.•Experiments and DFT calculations reveal the effect of Nd3+ doping on the energy band structure of the photocatalyst. Three-dimensional hierarchical rosette-shaped Bi3O4Br has been successfully prepared by a one-step hydrothermal method for the first time, in which the doping of Nd3+ into the matrix of Bi3O4Br induces abundant oxygen vacancies and triggers energy-band hybridization to produce new dopant levels, which can efficiently receive photo-excited electrons and inhibit the complexation of photogenerated carriers. Impressively, the doped energy levels act as “springboards” for photogenerated electron jumps, exacerbating the inhomogeneity of charge distribution and accelerating charge separation. In addition, the fine-tuning of Nd3+ improves the band structure and photocatalytic performance of Nd/Bi3O4Br. Notably, the unique 3D rosette-like Bi3O4Br could enhance the adsorption capacity of the catalyst and provide more opportunities for the introduction of Nd3+ to induce the generation of abundant oxygen vacancies. Both experimental and density functional theory (DFT) results reveal the synergistic effect of energy band hybridization and oxygen vacancies. In addition, comparative experiments showed that Nd/Bi3O4Br enhanced the maximum removal efficiency of heavy metal mercury by 29.66 % relative to Bi3O4Br under visible light. The present work reveals the reaction mechanism of photocatalytic oxidation for mercury removal, which provides a new direction for realizing energy conversion and environmental purification in the future.